This invention relates generally to a sewing machine for forming a knit shirt placket, and more specifically to a lock-stitch needle chuck and placket assembly formed using the needle chuck. The invention has particular application in the assembly of Allen Solley shirt plackets, such as that common in golf shirts and other casual knit shirts. The sewing machine of the present invention substantially eliminates the pucker typically formed at a bottom corner of the knit shirt placket, thus improving the aesthetic appearance of the shirt.
The process of forming a shirt placket requires precise sewing and cutting of the overlaid placket patch and shirt front. The placket patch is typically sewn to the shirt front using a conventional lock-stitch, double needle sewing machine with a center cutter located between and slightly to the rear of the needles. The double needles sew parallel lines of stitches in the placket patch and shirt front while the cutter cuts the fabric parts at a point between the stitch lines. Ideally, the stitch lines terminate at exact predetermined points such that the patch is properly sewn to the shirt front, and properly cut.
According to one prior art technique, the machine operator would manually feed and guide the overlaid placket patch and shirt front through the sewing machine, and attempt to stop the sewing motor at the exact moment the trailing end of the placket patch was reached. This manual technique was generally slow, and often produced rejects due primarily to human error. In an effort to overcome this problem, some prior art machines employed an electronic motor with stitch counting capability. The machine automatically stopped sewing after a predetermined stitch count. Although this machine was far more effective than the manual technique, it nevertheless suffered from many drawbacks and limitations. For example, stitch counting was unable to compensate for different size patches, placement variations, different stitch lengths, cloth puckering, and poor handling of the cloth by the machine operator.
As described in the Applicant""s prior issued patents, U.S. Pat. Nos. 5,862,767 and 5,868,090, these and other problems of the prior art were substantially resolved by utilizing a light transmitter and fiber optic cable to sense the end of the placket patch, and automatically stop operation of the sewing motor. This technique produced a consistently accurate stitch and cut. The signal receiving end of the fiber optic cable was secured in an opening formed in the throat plate of the sewing machine in an area outside of the sewing and cutting elements of the machine. The fiber optic cable does not interfere with operation of the sewing needles or cutter, yet is positioned sufficiently close to these elements to accurately determine the trailing edge of the placket patch and relay this information to a programmable motor controller to stop the machine at the desired point.
While the sewing machine described in the Applicant""s prior patents greatly improved the assembly of the placket patch and shirt front, there remained a need in the industry to improve the overall finished look of the shirt placket. A largely aesthetic problem common in most knit shirts is the slight puckering that occurs at the bottom corner of the shirt placket during wear. This puckering results from the inversion and folding of the placket patch after sewing and cutting. Through its research and experimentation, Applicant determined that by adding one or two extra stitches on one of the two parallel stitch lines made during formation of the placket assembly, the puckering formed at the bottom end of the finished placket was substantially eliminated.
Therefore, it is an object of the invention to provide a placket sewing machine which forms a substantially pucker-free shirt front.
It is another object of the invention to provide a lock-stitch needle chuck for use in a placket sewing machine, and adapted for sewing extra stitches along one of two parallel lines of stitches during formation of the placket assembly to substantially eliminate the pucker typically formed at the bottom end of the shirt placket in casual knit shirts.
It is another object of the invention to provide a method of forming a shirt placket assembly which substantially eliminates the pucker typically formed at the bottom end of the shirt placket in casual knit shirts.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a placket sewing machine for attaching a placket patch to a fabric part of a garment in overlying relation to form a multiple layer placket assembly. The placket sewing machine includes a base defining a working surface of the sewing machine, and including a fabric moving feed dog for moving the overlaid placket patch and fabric part downstream through the sewing machine. A reciprocating needle chuck has first and second needle openings formed in a staggered forward and rearward arrangement. First and second sewing needles are positioned within respective needle openings of the chuck. The sewing needles are adapted for carrying respective ends of thread into and through the overlaid placket patch and fabric part to form first and second parallel lines of stitches in the placket assembly. The first line of stitches extends a greater distance along the length of the overlaid placket patch and fabric part than the second line of stitches. A sewing motor is operatively connected to the needle chuck for actuating the chuck during operation of the sewing machine. A fabric cutter is located downstream of and centrally disposed between the first and second sewing needles for cutting the overlaid placket patch and fabric part after sewing.
According to another preferred embodiment of the invention, a motor controller is provided for controlling operation of the sewing motor and needle chuck.
According to another preferred embodiment of the invention, ply-sensing means are operatively connected to the motor controller for automatically stopping operation of the sewing motor and needle chuck upon sensing a trailing end of the placket patch.
According to another preferred embodiment of the invention, the ply-sensing means includes a transmitter mounted above the base of the sewing machine for transmitting a ply-sensing signal of sufficient intensity such that the signal is capable of penetrating the thickness of the fabric part, and is interrupted by the multi-layer thickness of the overlaid placket patch and fabric part.
According to another preferred embodiment of the invention, the ply-sensing means further includes a receiver located in the base of the sewing machine and in signal-passage alignment with the transmitter for receiving the signal of the transmitter through the fabric part. The transmitter and receiver are located respectively on opposite sides of the overlaid placket patch and fabric part. Upon interruption of the ply-sensing signal indicating a presence of both the placket patch and fabric part, the motor controller maintains operation of the sewing motor and needle chuck. Upon receiving the ply-sensing signal of the transmitter indicating an absence of the placket patch, the motor controller stops operation of the sewing motor and needle chuck.
According to another preferred embodiment of the invention, a throat plate is provided for supporting the overlaid placket patch and fabric part on the working surface of the base in an area of the first and second sewing needles. The throat plate defines an opening for accommodating passage of the reciprocating needles and movement of the feed dog.
According to another preferred embodiment of the invention, the throat plate includes a side extension located outside of an area of the sewing needles. The extension of the throat plate defines a port for holding the receiver in signal passage alignment with the transmitter during placket sewing operations.
In another preferred embodiment, the invention is a needle chuck adapted for use in a placket sewing machine for attaching a placket patch to a fabric part of a garment in overlying relation to form a multiple layer placket assembly. The needle chuck includes first and second needle openings formed in a staggered forward and rearward arrangement and adapted for holding first and second sewing needles. The sewing needles are adapted for carrying respective ends of thread into and through the overlaid placket patch and fabric part to form first and second parallel lines of stitches in the placket assembly. The first line of stitches extends a greater distance along the length of the overlaid placket patch and fabric part than the second line of stitches. Locking means holds the first and second sewing needles in a rigid fixed condition.
According to another preferred embodiment of the invention, the locking means includes respective set screws adapted for entering the needle chuck and engaging the sewing needles.
According to another preferred embodiment of the invention, cutter holding means holds a fabric cutter in a fixed rigid condition between the first and second needle openings.
In another preferred embodiment, the invention is a multiple layer placket assembly for being incorporated into a garment. The placket assembly includes a fabric part of a garment and a placket patch overlying the fabric part of the garment. First and second parallel lines of stitches are formed into and through the placket patch and fabric part to attach the placket patch and fabric part together. The first line of stitches extends a greater distance along the length of the overlaid placket patch and fabric part than the second line of stitches.
According to another preferred embodiment of the invention, a longitudinal cut is formed through the placket patch and fabric part in an area between the first and second line of stitches.
In another preferred embodiment, the invention is a method of forming a placket assembly including a placket patch and a fabric part of a garment. The method includes the steps of positioning the placket patch and fabric part in overlying relation on a working surface of a placket sewing machine. First and second ends of thread are then carried into and through the overlaid placket patch and fabric part to form first and second parallel lines of stitches in the placket assembly. The first line of stitches extends a greater distance along the length of the overlaid placket patch and fabric part than the second line of stitches. The overlaid placket patch and fabric part is then cut longitudinally in an area between the first and second lines of stitches.